GM Blazer/Jimmy/Typhoon/Bravada 1983-1993 Repair Guide

Timing Chain and Gears

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REMOVAL & INSTALLATION



1.9L Engine

See Figures 1, 2 and 3

The following procedure requires the use of the puller tool No. J-25031 or equivalent, and timing sprocket installation tool No. J-26587 or equivalent.

  1. Remove the timing (front) cover from the engine.
  2.  
  3. Lock the shoe on the automatic adjuster in the fully retracted position by depressing the adjuster lock lever.
  4.  

To remove the timing chain, it may be necessary to remove the camshaft sprocket. Before removing the timing chain, be sure to align the timing marks.

  1. Remove timing chain from the crankshaft sprocket.
  2.  
  3. Check the timing sprockets for wear or damage. If the crankshaft sprocket must be replaced, remove the sprocket and the pinion gear from crankshaft using the puller tool No. J-25031 or equivalent.
  4.  
  5. Check timing chain for wear or damage; replace as necessary. Measure distance "L" (40 links) with the chain stretched with a pull of approximately 22 lbs. (98 N). Standard "L" value is 15 in. (381mm); replace chain if "L" is greater than 15.16 in. (385mm).
  6.  
  7. Remove the automatic chain adjuster-to-engine bolt and the adjuster.
  8.  
  9. To check the operation of the automatic chain adjuster, push the shoe inwards, if it becomes locked, the adjuster is working properly. The adjuster assembly must be replaced if rack teeth are found to be worn excessively.
  10.  
  11. To remove the chain tensioner, remove the "E" clip and the tensioner. Check the tensioner for wear or damage; if necessary, replace it.
  12.  
  13. Inspect the tensioner pin for wear or damage. If replacement is necessary, remove the pin from the cylinder block using a pair of locking pliers. Lubricate the NEW pin tensioner with clean engine oil. Start the pin into block, then place the tensioner over the appropriate pin. Position the E-clip onto the pin, then (using a hammer) tap it into the block until clip just clears tensioner. Check the tensioner and adjuster for freedom of rotation on the pins.
  14.  
  15. Inspect the guide for wear or damage and plugged lower oil jet. If replacement or cleaning is necessary, remove the guide bolts, the guide and the oil jet. Install a new guide and upper attaching bolt. Install the lower oil jet and bolt, so that the oil port is pointed toward crankshaft.
  16.  

To install:
  1. Install the timing sprocket and the pinion gear (groove-side toward the front cover). Align the key groove with crankshaft key, then drive it into position using installation tool No. J-26587 or equivalent.
  2.  
  3. Turn the crankshaft so that key is turned toward the cylinder head-side (No. 1 and No. 4 pistons at TDC).
  4.  
  5. Install the timing chain, align the timing chain mark plate with the mark on the crankshaft timing sprocket. The side of the chain with the mark plate is on the front-side and the side of chain with the most links between mark plates is on the chain guide-side. Keep the timing chain engaged with the camshaft timing sprocket until the camshaft timing sprocket is installed on the camshaft.
  6.  
  7. Install the camshaft timing sprocket so that it's marked-side faces forward and it's triangular mark aligns with the chain mark plate.
  8.  
  9. Install the automatic chain adjuster.
  10.  
  11. Release the lock by depressing the shoe on adjuster by hand, and check to make certain the chain is properly tensioned when the lock is released.
  12.  
  13. Install the timing cover assembly.
  14.  



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Fig. Fig. 1: Timing chain guide and tensioner - 1.9L engine



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Fig. Fig. 2: Timing chain alignment and installation - 1.9L engine



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Fig. Fig. 3: Inspecting the timing chain for wear

2.0L Engine

See Figure 4

The following procedure requires the use of the spring compressor tool No. J-33875 or equivalent, the gear puller tool No. J-22888-20 or equivalent.

  1. Remove the timing cover from the engine.
  2.  
  3. Rotate the crankshaft to position the No. 4 piston on TDC of the compression stroke; the marks on the camshaft and crankshaft sprockets should be in alignment and positioned closest together in their travel.
  4.  
  5. Loosen the timing chain tensioner nut (as far as possible) without actually removing it.
  6.  



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Fig. Fig. 4: Timing mark alignment - 2.0L engine

  1. Remove the camshaft sprocket-to-camshaft bolts and the sprocket; remove the timing chain with the sprocket. If the sprocket does not slide from the camshaft easily, a light blow with a soft mallet at the lower edge of the sprocket should dislodge it.
  2.  
  3. Using the gear puller tool No. J-22888-20 or equivalent, remove the crankshaft sprocket.
  4.  

To install:
  1. Using a putty knife, clean the gasket mounting surfaces. Inspect the timing chain and the sprocket teeth for wear and/or damage; replace the parts, if necessary.
  2.  
  3. Install the crankshaft sprocket onto the crankshaft, position the timing chain over the camshaft sprocket and then around the crankshaft sprocket. Make sure that the marks on the two sprockets are aligned. Lubricate the thrust surface with Molykote® or an equivalent pre-lube.
  4.  
  5. Align the dowel in the camshaft with the dowel hole in the sprocket and then install the sprocket onto the camshaft. Torque the camshaft sprocket-to-camshaft bolts to 66-88 ft. lbs. (90-120 Nm).
  6.  
  7. Lubricate the timing chain with clean engine oil. Using the spring compressor tool No. J-33875 or equivalent, position the tangs under the sliding block and pull the tool to compress the spring. Tighten the chain tensioner.
  8.  
  9. Install the timing cover to the engine.
  10.  

2.8L and 4.3L Engine

See Figures 5, 6, 7, 8, 9 and 10

The following procedure requires the use of the Crankshaft Sprocket Removal tool No. J-5825-A or equivalent, and the Crankshaft Sprocket Installation tool No. J-5590 or equivalent.

  1. Remove the timing cover from the engine.
  2.  
  3. Rotate the crankshaft until the No. 4 cylinder is on the TDC of it's compression stroke and the camshaft sprocket mark aligns with the mark on the crankshaft sprocket (facing each other at a point closest together in their travel) and in line with the shaft centers.
  4.  



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Fig. Fig. 5: Timing mark alignment - 2.8L engine



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Fig. Fig. 6: Timing mark alignment - 4.3L engine

  1. Remove the camshaft sprocket-to-camshaft nut and/or bolts, then remove the camshaft sprocket (along with the timing chain). If the sprocket is difficult to remove, use a plastic mallet to bump the sprocket from the camshaft.
  2.  

The camshaft sprocket (located by a dowel) is lightly pressed onto the camshaft and should come off easily. The chain comes off with the camshaft sprocket.

  1. If necessary use J-5825-A or an equivalent crankshaft sprocket removal tool to free the timing sprocket from the crankshaft.
  2.  

To install:
  1. Inspect the timing chain and the timing sprockets for wear or damage, replace the damaged parts as necessary.
  2.  



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Fig. Fig. 7: Removal (top) and installation of the crankshaft timing gear

  1. Using a putty knife, clean the gasket mounting surfaces. Using solvent, clean the oil and grease from the gasket mounting surfaces.
  2.  
  3. If removed, use J-5590, or an equivalent crankshaft sprocket installation tool and a hammer to drive the crankshaft sprocket onto the crankshaft, without disturbing the position of the engine.
  4.  

During installation, coat the thrust surfaces lightly with Molykote® or an equivalent pre-lube.

  1. Position the timing chain over the camshaft sprocket. Arrange the camshaft sprocket in such a way that the timing marks will align between the shaft centers and the camshaft locating dowel will enter the dowel hole in the cam sprocket.
  2.  
  3. Position the chain under the crankshaft sprocket, then place the cam sprocket, with the chain still mounted over it, in position on the front of the camshaft. Install and tighten the camshaft sprocket-to-camshaft retainers to 17 ft. lbs. (23 Nm) for 2.8L engines or to 21 ft. lbs. (28 Nm) for 4.3L engines.
  4.  
  5. With the timing chain installed, turn the crankshaft two complete revolutions, then check to make certain that the timing marks are in correct alignment between the shaft centers.
  6.  
  7. Install the timing cover.
  8.  



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Fig. Fig. 8: Use the damper bolt to turn the crankshaft in the normal direction of engine rotation until the timing marks are aligned



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Fig. Fig. 9: The sprocket timing marks should align with each other and the reference tabs on the timing chain tensioner



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Fig. Fig. 10: Loosen and remove the camshaft sprocket bolts in order to remove the sprocket and chain

 
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